1. Field of the Invention
The present invention relates to a technique for displaying an ophthalmologic image for use in, for example, an ophthalmologic medical care.
2. Description of the Related Art
An imaging apparatus referred to as an optical coherence tomography (hereinafter referred to as “OCT”) has enabled acquisition of a three-dimensional retina image formed by volume rendering based on a plurality of two-dimensional tomographic images obtained by scanning an entire retina. It is known that a large number of fundus diseases such as glaucoma cause abnormality in the structure of a retina, and therefore the OCT is expected to be effective for a diagnosis of a disease and a follow-up observation in the ophthalmologic medical field. Further, in recent years, the OCT has been used in imaging not only a fundus diagnosis but also an anterior eye portion such as a cornea.
In a tomographic image, a value of a reflection intensity of light from, for example, a retina is observed as an image. Therefore, a tomographic image is suitable for an observation of a tissue, but may be difficult to be used to grasp, for example, a change in a tissue over time, an overall spread of a disease, and a portion to be focused on, without an additional help.
Japanese Patent Application Laid-Open No. 2009-66015 discusses a technique which displays a tomographic image and layer thickness distribution information arranged side by side. Using the technique, the layer thickness distribution information and the tomographic image can be compared. Japanese Patent Application Laid-Open No. 2009-66015 further discusses a method for indicating a vascular territory. If a vessel exists in a retina, the light of the OCT cannot reach a deep portion, resulting in generation of a low-quality tomographic image. Therefore, Japanese Patent Application Laid-Open No. 2009-66015 indicates a need for a user to observe a retina while taking this matter into consideration.
However, the method discussed in Japanese Patent Application Laid-Open No. 2009-66015 can be used for comparison between a tomographic image and a layer thickness, and it is difficult to grasp, for example, how much a lesion has progressed from the tomographic image by this method.